Hi,
On 21/06/18 23:19, Enric Balletbo i Serra wrote:
> When the devfreq driver and the governor driver are built as modules,
> the call to devfreq_add_device() or governor_store() fails because the
> governor driver is not loaded at the time the devfreq driver loads. The
> devfreq driver has a build dependency on the governor but also should
> have a runtime dependency. We need to make sure that the governor driver
> is loaded before the devfreq driver.
>
> This patch fixes this bug by adding a try_then_request_governor()
> function. First tries to find the governor, and then, if it is not found,
> it requests the module and tries again.
>
> Fixes: 1b5c1be2c88e (PM / devfreq: map devfreq drivers to governor using name)
> Signed-off-by: Enric Balletbo i Serra <enric.balle...@collabora.com>
> ---
> Changes in v2:
> - Add a new function to request the module and call that function from
> devfreq_add_device and governor_store.
>
> drivers/devfreq/devfreq.c | 69 +++++++++++++++++++++++++++++++--------
> 1 file changed, 56 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 0b5b3abe054e..dfdf9fc9c212 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -11,6 +11,7 @@
> */
>
> #include <linux/kernel.h>
> +#include <linux/kmod.h>
> #include <linux/sched.h>
> #include <linux/errno.h>
> #include <linux/err.h>
> @@ -221,6 +222,46 @@ static struct devfreq_governor
> *find_devfreq_governor(const char *name)
> return ERR_PTR(-ENODEV);
> }
>
> +/**
> + * try_then_request_governor() - Try to find the governor and request the
> + * module if is not found.
> + * @name: name of the governor
> + *
> + * Search the list of devfreq governors and request the module and try again
> + * if is not found. This can happen when both drivers (the governor driver
> + * and the driver that call devfreq_add_device) are built as modules.
> + *
> + * Return: The matched governor's pointer.
> + */
> +static struct devfreq_governor *try_then_request_governor(const char *name)
> +{
> + struct devfreq_governor *governor;
> + int err = 0;
> +
> + mutex_lock(&devfreq_list_lock);
> +
> + governor = find_devfreq_governor(name);
> + if (IS_ERR(governor)) {
> + mutex_unlock(&devfreq_list_lock);
> +
> + if (!strncmp(name, DEVFREQ_GOV_SIMPLE_ONDEMAND,
> + DEVFREQ_NAME_LEN))
> + err = request_module("governor_%s", "simpleondemand");
> + else
> + err = request_module("governor_%s", name);
> + if (err)
> + return NULL;
> +
> + mutex_lock(&devfreq_list_lock);
> +
> + governor = find_devfreq_governor(name);
> + }
> +
> + mutex_unlock(&devfreq_list_lock);
> +
> + return governor;
> +}
> +
> static int devfreq_notify_transition(struct devfreq *devfreq,
> struct devfreq_freqs *freqs, unsigned int state)
> {
> @@ -644,17 +685,16 @@ struct devfreq *devfreq_add_device(struct device *dev,
>
> mutex_unlock(&devfreq->lock);
>
> - mutex_lock(&devfreq_list_lock);
> - list_add(&devfreq->node, &devfreq_list);
> -
> - governor = find_devfreq_governor(devfreq->governor_name);
> + governor = try_then_request_governor(devfreq->governor_name);
> if (IS_ERR(governor)) {
> - dev_err(dev, "%s: Unable to find governor for the device\n",
> + dev_err(dev,
> + "%s: Unable to find governor for the device\n",
> __func__);
Just noticed this unneeded change.
> - err = PTR_ERR(governor);
and that I broke the error set. I will send a v3.
> - goto err_init;
> + goto err_unregister;
> }
>
> + mutex_lock(&devfreq_list_lock);
> +
> devfreq->governor = governor;
> err = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_START,
> NULL);
> @@ -663,14 +703,16 @@ struct devfreq *devfreq_add_device(struct device *dev,
> __func__);
> goto err_init;
> }
> +
> + list_add(&devfreq->node, &devfreq_list);
> +
> mutex_unlock(&devfreq_list_lock);
>
> return devfreq;
>
> err_init:
> - list_del(&devfreq->node);
> mutex_unlock(&devfreq_list_lock);
> -
> +err_unregister:
> device_unregister(&devfreq->dev);
> err_dev:
> if (devfreq)
> @@ -988,12 +1030,13 @@ static ssize_t governor_store(struct device *dev,
> struct device_attribute *attr,
> if (ret != 1)
> return -EINVAL;
>
> - mutex_lock(&devfreq_list_lock);
> - governor = find_devfreq_governor(str_governor);
> + governor = try_then_request_governor(str_governor);
> if (IS_ERR(governor)) {
> - ret = PTR_ERR(governor);
> - goto out;
> + return PTR_ERR(governor);
> }
> +
> + mutex_lock(&devfreq_list_lock);
> +
> if (df->governor == governor) {
> ret = 0;
> goto out;
>
